The invention relates to a method for describing the three-dimensional path of an industrial processing machine, such as a machine tool, a robot and the like.
Published European patent specification EP 04 17 337 A1 describes a method for controlling a numerically controlled machine or a robot using a spline interpolation. The axes parameters (x, y) are hereby defined as functions of a path parameter (s). The velocity along the path is controlled by expanding the paths of the functions or by sampling the paths with different step lengths. Alternatively, the support points for the spines can be varied as a function of the path parameters to reflect a desired velocity profile.
Disadvantageously, when using a spline interpolation, only two axes parameters can be selected for a two-dimensional representation in a fixed Cartesian coordinate system. This restricts the use of spline interpolations for controlling the path of numerically controlled machines or robots. One example for a conventional application of spline interpolations can be found in the user reference and programming manual “SINUMERIK System 800”, revision 09.88, by Siemens AG (Order No. 6ZB5 410-7BA01-0BA0).
One example of a numerically controlled machine is a machine tool, in particular a turning machine or a lathe. The turning machine has at least a rotation function. For turning applications, eccentric contours are of particular interest. An eccentric contour, which can also be divided into different sectors, is characterized by a radial distance r which is a dependent variable and geometrically controlled by one or two independent variables z and c. The value z is here the position on a z-axis, whereas the value c represents an angular position. The result is a function f for the radial distance r with r=f(z, c). Different discrete tables are defined for r=f(c) for a number of sectors and stored in a numerical controller and recalled for defined positions on the z-axis. In other words, at certain positions on the z-axis, a switchover to the tables occurs. The tables are quite large and require a large memory space. Moreover, this method for motion control is not capable of completely and continuously describing a freeform surface for turning, because the tables are constructed two-dimensionally and can only be changed in a discrete fashion.
It would therefore be desirable and advantageous to provide an improved device for a three-dimensional path description of an industrial processing machine, which obviates prior art shortcomings and obviates the need for storing and manipulating tables with large datasets.